JPH05345666A - Production of formed carbon material - Google Patents

Abstract

PURPOSE:To form a mosaic texture in a formed carbon material and to improve the mechanical strength of the material in high efficiency at a low cost by mixing a specific treated material with a powdery thermosetting resin and compression-molding under heating. CONSTITUTION:A powdery meso-phase pitch (A) having a softening point of 100-400 deg.C determined by Mettler method is obtained by selecting particles of coal pitch, etc., passing through a sieve having a sieve opening of about 150mum. The component A is oxidized by heating in air to obtain an oxidized product (B) having an oxygen content of 40-20wt.%. The component B is mixed with a thermosetting resin (C) such as urea resin at a weight ratio of (1-4):(9-6) and pressed to obtain a formed article (D). The article D is hardened at 100-300 deg.C and carbonized or graphitized to produce the formed carbon material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carbon molding material having a fine mosaic structure and excellent mechanical properties.
Applications are expected in a wide range of fields such as chemistry.

[0002]

2. Description of the Related Art Carbon materials have been used in a wide range of fields as high temperature materials because of their excellent high temperature mechanical properties, high thermal and electrical conductivity, and excellent sliding properties. The characteristics vary depending on the raw material and the manufacturing method, but among them, those that form a fine mosaic structure (hereinafter referred to as “mosaic structure”) in which an optically isotropic structure and an anisotropic structure are particularly excellent in mechanical properties. It is known that For this reason, attempts have been made to develop a technology for producing a carbon material having a fine mosaic structure. A pitch, which is a typical anisotropic carbon raw material, and a thermosetting resin, which is a typical isotropic carbon raw material, have been tried. There is known a method of producing by using as a raw material a mixture of and in a molten state or a solution state. In these methods, when the pitch and the thermosetting resin are mixed to control the optical anisotropy of the carbon material, it is important to make both raw materials compatible with each other. Therefore, the following two types of techniques have been disclosed.

A method of dissolving a solvent-soluble component in a pitch and a thermosetting resin in a solvent having a strong dissolving power such as pyridine and mixing them (Ogawa et al., J. Mat. Sci. Vol. 20,
17-22, 1985). However, this method requires a step of removing the solvent and drying after mixing the raw materials,
The process becomes complicated. Further, the carbon material precursor produced by this method is soluble in a solvent and may be melted in the carbonization step. Therefore, heat stabilization (infusibilization) treatment is indispensable in order to carbonize in a shape-imparted state. In addition, it is difficult to sufficiently perform heat stabilization treatment, and foaming easily occurs in the carbonization process, which makes it difficult to form a dense carbon material.

A method in which a solvent-soluble component of pitch and a thermosetting resin are mechanically mixed in a powder state and carbonized under a pressure of 10 MPa or more (Inagaki et al., Carbon Vo.
l. 28,559-564,1990). It has been proposed as a method of avoiding the problems listed in the method, the main point is that the low molecular weight component contained in the pitch or the low molecular weight component generated in the carbonization step, the pitch and the thermosetting resin under pressure. The mediation of the interaction between the two forms a uniform mosaic tissue. In this method, it is indispensable to carbonize under low pressure in order to prevent low molecular weight components that play an important role from leaking out of the system in the carbonization process.
Equipment that can withstand high pressure is required.

[0005]

The present invention has been made in view of the above problems, and its purpose is to:
An object of the present invention is to provide a method for inexpensively and efficiently producing a carbon molding material having a fine mosaic structure and excellent mechanical strength.

[0006]

Means for Solving the Problems The production method of the present invention capable of solving the above-mentioned problems is as follows: (a) a powdery mesophase pitch having a softening point of 100 ° C. or higher and 400 ° C. or lower measured by the Mettler method is used. The oxidization treatment was performed so that the content is 4 to 20% by weight, and (b) the powdery thermosetting resin was mixed in a weight ratio of 1: 9 to 4: 6, and 100
The main point is to perform pressure molding in the temperature range of up to 300 ° C.

[0007]

The mesophase pitch (hereinafter sometimes referred to as “soft mesophase pitch”) having a softening point of 100 ° C. or higher and 400 ° C. or lower, which is mainly used as a raw material for carbon fibers and measured by the Mettler method, has a condensed aromatic ring of constituent molecules. They are oriented parallel to each other and are particularly suitable as precursors for anisotropic carbon materials. Further, since the soft mesophase pitch has a higher softening point due to oxidation, it can be carbonized without being substantially melted by performing sufficient oxidation treatment. The present inventors
As a result of detailed study of the carbonization process using powdered mesophase pitch oxidized under various conditions as a raw material, it is softened to such an extent that the pitch powders are fused to each other, but the shape can be maintained without flowing out in the carbonization process. It was found that oxidizing conditions existed. Further, the oxidized pitch (hereinafter referred to as “oxidized pitch”) contains oxygen-containing functional groups such as carbonyl group, carboxyl group, and quinone structure, and these functional groups exist almost stably at 250 ° C. or lower. , 30
It was found that decomposition occurs at a temperature of 0 ° C or higher to cause a polymerization reaction.

On the other hand, the polymerization reaction of the thermosetting resin (hereinafter sometimes referred to as "resin") proceeds at a sufficient rate even at a temperature of 300 ° C or lower. Further, since the thermosetting resin chemically interacts with the oxygen-containing functional group in the oxidized pitch, if the resin is cured at a temperature below the temperature at which the oxygen-containing functional group in the pitch begins to decompose, the resin and the pitch And a complex is formed. The present inventors have found that the thus obtained composite is a carbon material that can be carbonized without melting even without subjecting it to a heat stabilization treatment, and is a carbon material having a fine optical mosaic structure. The invention was completed.

The reasons why the pitch and the thermosetting resin used as the raw materials in the present invention are limited to powder form will be described below. First, as the liquid pitch, there may be mentioned one that is heated and melted, or one that is dissolved in a solvent. However, these liquid pitches are not preferable as a raw material for a molded product because they melt and foam in the carbonization step. Further, when a liquid thermosetting resin is used, it is difficult to mix it with a powdery pitch, or it is difficult to cure and carbonize the molded product while maintaining its shape. Therefore, the raw material pitch and the thermosetting resin are both limited to powder.

The pitch used in the present invention is not particularly limited in its origin and kind as long as it is a soft mesophase pitch, that is, a mesophase pitch that can be melted, and coal-based, petroleum-based or aromatic hydrocarbons are present in the presence of a catalyst. Examples include polymerized products. The reason why the pitch of the present invention is limited to the soft mesophase pitch is as follows. First,
The one in which isotropic pitch is oxidized and made infusible is unsuitable for the formation of a mosaic texture because the anisotropic texture is not sufficiently expressed. On the other hand, mesophase pitch having no meltability is not suitable for forming a uniform mosaic structure because even if it is oxidized to a fairly light level, it does not soften to the extent that pitch particles are fused together in the carbonization step. The particle size composition of the soft mesophase pitch powder may be appropriately determined in consideration of the size of the molding material, the purpose of use, etc. However, if the particle size is too large, it is not desirable for forming a fine mosaic structure. The particle size is preferably such that it can pass through a sieve. The method of oxidizing these soft mesophase pitches is not particularly limited, and may be performed according to a conventional method such as oxidation by heating in an air atmosphere. The degree of oxidation of the soft mesophase pitch powder can be evaluated by the oxygen content in the pitch, but in the present invention, an oxygen content of 4 to 20% by weight is preferable. When the oxygen content is less than 4% by weight, the softening point of the mesophase pitch is insufficiently increased and it is difficult to maintain the shape in the carbonization step. On the other hand, when the oxygen content exceeds 20% by weight, the pitch is not sufficiently softened in the carbonization step, and the fusion between the pitch particles becomes insufficient.

The thermosetting resin used in the present invention may be of any type as long as it is in powder form, for example, urea resin, melanin resin, phenol resin, epoxy resin, unsaturated polyester resin, alkyd resin, urethane resin, etc. Is mentioned. It is preferable that the resin powder has an average particle diameter of 100 μm or less because a finer particle diameter facilitates homogeneous mixing with the oxidized pitch.

The mixing ratio of the thermosetting resin to the oxidized pitch is preferably 1: 9 to 4: 6 by weight. When the mixing ratio of the thermosetting resin is less than 1: 9, the amount of raw material that gives isotropic carbon is small, which is unsuitable for forming a mosaic structure. On the other hand, when the mixing ratio of the resin is larger than 4: 6, the isotropic structure and the anisotropic structure are separated to form a heterogeneous material, and sufficient mechanical strength cannot be obtained.

The molding temperature of the mixture of the powdery thermosetting resin and the oxidized pitch is preferably 100 to 300 ° C.
If it is less than 100 ° C., the progress of the polymerization reaction of the thermosetting resin is slow and the softening of the oxidized pitch is insufficient, so that a homogeneous oxidized pitch-resin composite cannot be molded. on the other hand,
If the molding temperature exceeds 300 ° C., the polymerization of the resin will be too fast to form a homogeneous composite. Further, the decomposition of the oxygen-containing functional group in the oxidized pitch also occurs rapidly, and the interaction between the resin and the pitch is reduced, which is not suitable for forming a mosaic structure. The conditions other than the temperature at the time of pressure molding may be appropriately determined according to a conventional method.

Thus, the molding material obtained by the method of the present invention can be post-cured if necessary and carbonized or graphitized into a carbon material having excellent mechanical strength.

[0015]

The present invention will be described in more detail with reference to the following examples, but the following examples do not limit the present invention.
All changes and modifications made without departing from the spirit of the above and the following are included in the technical scope of the present invention.

Example 1 Soft mesophase pitch prepared by subjecting a coal-based hard pitch to a hydrogenation treatment under a reduced pressure was crushed, and each soft-mesophase pitch shown in Table 1 was heated at a heating rate of 1 ° C./min in an air atmosphere. Oxidation treatment was performed up to the temperature. 75 g of each pitch oxidized under the above conditions was mixed well with 25 g of powdered phenol resin,
Using a mold heated to 150 ℃, thickness 15mm x width 50mm
C. A plate having a length of 150 mm was pressure-molded. The bulk density of each of the obtained molded bodies was 1.33 g / cm ³ . Each molded product was post-cured at 200 ° C. for 2 hours and then graphitized at 2400 ° C. in an inert atmosphere under normal pressure. The results are shown in Table 1.

[0017]

[Table 1]

As can be seen from Table 1, when the oxygen content in the pitch after the oxidation treatment is less than 4% by weight (No.
In 1), molding was possible, but the shape of the molded body could not be maintained due to partial foaming in the graphitization process. In addition, when the oxygen content in the oxidized pitch exceeded 20% by weight (No. 5), molding was possible, but cracks occurred in the graphitization process. On the other hand, in the examples (Nos. 2 to 4) satisfying the specified requirements of the present invention, a dense carbon material was obtained without melting or foaming even when graphitized under normal pressure. Moreover, when the optical texture was observed, all of them showed a fine mosaic texture.

Example 2 Soft mesophase pitch synthesized by polymerizing naphthalene in the presence of an acid catalyst was pulverized and crushed in a nitrogen atmosphere containing 10 vol% oxygen at a heating rate of 0.5 ° C./min to 230.
Oxidation treatment was performed up to ° C. The elemental analysis values of the pitch after the oxidation treatment are C: 87.2 wt%, H: 3.2 wt%, O: 9.
It was 5% by weight and 0.1% by weight. The obtained oxidized pitch and the powdered phenolic resin were mixed in the proportions shown in Table 2 and pressure-molded in the same manner as in Example 1. The bulk density of each of the obtained molded bodies was 1.33 g / cm ³ . Each molded body was post-cured and graphitized under the same conditions as in Example 1.
The results are shown in Table 2.

[0020]

[Table 2]

As is clear from Table 2, in the examples (Nos. 7 to 9) satisfying the specified requirements of the present invention, the molding state was good, and a dense carbon material was obtained after graphitization. The optical structures after graphitization were all dense mosaic structures. On the other hand, the mixing ratio of resin and oxide pitch is 0.5: 9.5.
No. In No. 6, cracking occurred during molding. In addition, No. 1 having a mixing ratio of 4.5: 5.5. In No. 10, after the graphitization, the optically isotropic structure and the anisotropic structure were separated and existed separately, and the mosaic structure was not obtained.

Example 3 Oxide pitch was prepared under the same raw materials and conditions as in Example 2.
Powdered phenolic resin and this oxidized pitch were mixed at a ratio of 2: 8, and the thickness was 15 mm and the width was 50 under the temperature conditions shown in Table 3.
A plate having a size of mm × 100 mm was pressure-molded using a mold.
The obtained molded body was post-cured and graphitized in the same manner as in Example 1. The results are shown in Table 3.

[0023]

[Table 3]

As is clear from Table 3, in the examples satisfying the specified conditions of the present invention (Nos. 12 to 14), the molding state was good, and a dense carbon material was obtained after graphitization. The optical structure after graphitization was a fine mosaic. Meanwhile, 80 ° C
No. No. No. 11 could not make a molded body. In addition, No. In No. 15, although a molded body was formed, a cured film of phenol resin was formed on the surface. When it was graphitized, isotropic carbon was found in the vicinity of the surface, and numerous cracks were formed.

Example 4 Soft mesophase pitch prepared by heat-treating FCC residue was pulverized and crushed in air at a temperature rising rate of 1 ° C./min to 25
It was oxidized to 0 ° C. Elemental analysis value after oxidation is C: 8
It was 5.1% by weight, H: 3.6% by weight, O: 10.1% by weight, and others: 1.2% by weight. A powdery bismaleimide resin (30 g) and this oxidized pitch (70 g) were mixed well and a plate-shaped molded body was produced in the same manner as in Example 1. This molded product was post-cured at 220 ° C. for 2 hours and then 2400
Graphitized at ℃. A carbon form having a bulk density of 1.56 g / cm ³ showing a fine mosaic structure could be obtained.

[0026]

The present invention is configured as described above,
It has become possible to provide a method for inexpensively and efficiently producing a carbon molding material having a fine mosaic structure. Further, the molding material can be made into a carbon material having a dense structure and excellent mechanical strength by performing post-curing, carbonization, and graphitization as required.

Claims (1)

[Claims] 1. A method for producing a carbon molding material, comprising:
The powdery mesophase pitch having a softening point measured by the Mettler method of 100 ° C. or higher and 400 ° C. or lower has an oxygen content of 4
And those which have been subjected to an oxidation treatment so as to be up to 20% by weight,
(b) A method for producing a carbon molding material, which comprises mixing powdery thermosetting resin in a weight ratio of 1: 9 to 4: 6 and press-molding in a temperature range of 100 to 300 ° C. ..